Previous work suggests that arachidonic acid of ovarian and uterine origin may play an important role in determining the steroidogenic potencies of both the theca interna and granulosa-derived cells that make up the corpus luteum. Therefore, we plan to determine the influence of arachidonic acid, FSH and LH on the steroidogenic potencies of each of these cell types, cultured alone and together, at each developmental stage from the preovulatory follicle to the mature corpus luteum. Since free arachidonate is thought to be the rate limiting step in evolution of the "cascade" of products derived from arachidonic acid, we also plan to carry out in vitro studies on factors which control the release of free arachidonic acid in luteal tissue and stimulate its incorporation into the cyclooxygenase pathway. Factors to be studied include oxytocin, arginine vasopressin, and the blocking drugs indomethacin and mepacrine. The effects of hydrogen peroxide, catalase and glutathiome peroxidase on activation of the cyclooxygenase system of bovine luteal cells will be studied. In in vivo studies, we will examine the extent to which the uterus and ovaries each contribute to total arachidonic acid production during the estrous cycle and will study the question of whether any of the "cascade" of products derived from arachidonic acid in the uterus have luteotrophic, rather than luteolytic, effects. We also plan to determine the effects of removal of the uterine caruncles on corpus luteum function.